FOREIGN CORRESPONDENCE. 
347 
carbonate of magnesia, which crystallizes in rhomboid laminao of a 
pearly lustre. 
The cavities of the Roman masonry contain Hyalite and other varieties 
of Opal. Arfagonite is also found in these cavities ; the samples are 
bipyramidal crystals, very acute, resembling those found in the iron- 
beds of Framont and certain basalt formations. Calcareous-spar is seen 
mixed with the crystals of Chabasite before mentioned, and in the same 
cavities are observed small crystals of Fluor-spar, which have, in some 
places, their usual and beautiful violet tints. We must add that 
Professor Nickles, of Nancy, has very recently discovered fluorine in 
the mineral waters of Plombieres. Does the presence of this fluorine 
(contained in the water in shape of fluorides) explain that of Daubree's 
crystals of fluor-spar, or do the latter account for the discovery made by 
Nickles ? There can be hardly any doubt that it is the presence of 
certain fluorides in the waters of Plombieres that has given rise to the 
formation of the Blue- John or fluor-spar seen by M. Daubree,* by their 
action upon the lime of the Roman cement. 
In certain cavities and fissures where the Roman cement is exposed 
to a direct stream of warm water, a gelatinous substance is precipitated, 
which, by contact with the air, hardens, becomes quite opaque, and as 
white as snow. This substance analysed by M. Daubree, turns out to 
be a new mineral, a silicate of lime, to which he attributes ihe 
composition 
CaO Si 02 + 2 HO 
Silicate of lime + water. 
He calls it Plomhierite. 
In spite of the extreme hardness of the Roman masonry, it gives, 
nevertheless, access to the mineral water, which not only penetrates it 
in all directions, but actually passes through it. This passage is very 
slow, but continuous, and permits the chemical reactions which take 
place to multiply slowly for an immense space of time — an experimental 
element which modern chemists are in the habit of neglecting, but 
which the old alchymists knew well how to take into consideration.j- 
That time plays an important part in those essays by which we en- 
deavour to imitate natural productions, is seen by those beautiful 
experiments of M. Daubree's, to which we have before referred, and in 
• M. Jutier has just discovered at PlombiSres a large vein of Fluor-spar in the 
granite, which is traversed by the mineral waters, and whence doubtless these 
waters derive their soluble fluorides, which coming in rontact with the lime of the 
masonry are transformed anew into fluor-spar. — T. L. P. 
t Hortulanus, in the sixteenth century, says that to procure the Philosopher's 
Stone, " On fait digerer pendant douze jours des suer de mercuriale, de pourpier," 
&c. The celebrated alchymist Geber says, " I have seen mines of copper from 
which particles of this metal were carried away by a current of water. This 
water having dried up, the atoms of copper remained three years in the dry 
sand. I discovered that at the end of this time they had been cooked and digested 
by the heat of the sun and changed into laminae of pure gold. By imitating nature 
we produce the same transformation." HoefFer, in his " History of Chemistry," 
say that experiments begun by certain alchymists of the middle ages were often 
transmitted from father to son as an inheritance ; and that the son, not having 
lived long enough to terminate them, left them by will to his children. — T. L. P. 
2 D 2 
